It is known that crude hypothalmic preparations will inhibit the secretion of the growth hormone, somatotropin. The somatotropin-release-inhibiting factor (SRIF) responsible for this activity was isolated and its structure elucidated by Brazeau et al., Science, 179, 77 (1973) as: ##STR2## This tetradecapeptide is commonly referred to as somatostatin.
Somatostatin has also been found to inhibit the thyrotropin releasing hormone-induced release of thyrotropin in vivo in humans (Siler et al., J. Clin. Endocrinol. Metab., 38, 742, 1974), as well as inhibiting insulin (Mortimer et al., Lancet, 1, 697, 1974; Yen et al., New England J. Med., 290, 935, 1974); glucagon (Ginch et al., New England J. Med., 291, 544, 1974; Mortimer et al., ibid.) and gastrin (Bloom et al. Lancet, 2, 1106, 1974) secretion in vivo in humans. A direct somatostatin effect in the pancreatic cells or stomach has been confirmed under in vitro conditions for insulin (Mortimer et al., ibid), glucagon (Gerich et al., Endocrinology, 96, 749, 1975; Johnson et al., Endocrinology, 96, 370, 1975) and gastrin (Hayes et al., Endocrinology, 96, 1374, 1975).
In U.S. Pat. No. 4,061,626, somatostatin, D-Lys.sup.4 -SRIF and D-Ala.sup.2, D-Lys.sup.4 -SRIF are disclosed as gastric acid secretion inhibitors, as well as inhibitors of growth hormone, glucagon and insulin secretion. U.S. Pat. No. 4,062,816 discloses the activity of D-Ala.sup.5 -SRIF as an inhibitor of gastric acid secretion as well as an inhibitor of growth hormone secretion. Lippmann et al., Pharmac. Res. Comm., 8, 445 (1976) discloses gastric acid secretion inhibition by somatostatin and several analogs.
The present invention relates to a novel synthetic polypeptide which does not suppress insulin or glucagon, but selectively suppresses gastric secretion, and which may be characterized as an analog of somatostatin.